Secondary blasting charge and container therefor

ABSTRACT

A secondary blasting charge for removing &#39;&#39;&#39;&#39;hang-ups&#39;&#39;&#39;&#39; of ore, protruding rock formations, and other problem formations in mines and other blasting areas, comprises a molded plastic container designed to be supported on a pole or prop stick and capable of holding a blasting charge of adequate size and suitable configuration. A hole or socket element, which can be formed integrally with the container, is provided for receiving a supporting stick or pole. It serves also to house a primer or booster in detonating position within the charge and can serve also as a closure for a filler opening.

0 United States Patent 1151 3,638,570 Johnson 1 1 Feb. 1, 1972 [54] SECONDARY BLASTING CHARGE AND 2,911,910 11/1959 Welsh, Jr. ..102/22 X CONTAINER THEREFOR 3,208,381 9/1965 Kihlstrom et a1. 102/30 3,431,848 3/1969 Foster ..102/24 [721 :3? Lake 3,472,166 10/1969 Dowling ..102/24 [73] Assignee: lnterlnountain Research and Engineering Primary ExaminerVerlin R. Pendegrass Co., Inc. ArtorneyEdwin M. Thomas [22] Filed: Feb. 28, 1969 ABSTRACT 21 A LN 803,206 l 1 pp 0 A secondary blastlng charge for removmg hangups" of ore, protruding rock formations, and other problem formations in US. Cl. mines and other areas comprises a molded plasti [5 l 1 f Cl 1 A 3/00 container designed to be supported on a pole or' prop stick and [58] Field of Search ..102/21 .4, 22-24, capable of holding a blasting charge of adequate size and 30 suitable configuration. A hole or socket element, which can be formed integrally with the container, is provided for receiving [56] Reierences cued a supporting stick or pole. It serves also to house a primer or UNITED STATES PATENTS booster in detonating position within the charge and can serve also as a closure for a filler opening. 3,306,200 2/1967 Branseum et al ..102/24 1,571,122 l/ l 926 Hutton 102/26 1 Claims, 6 Drawing Figures PATENTEU FEB 1 B72 AVAYAVAAVA AVAYAVAVAYAYAYA VAYAYAYAYAYAVAY Hagan A I r @YAY Emma" AvAu/ INVENT OR 64 Yuan/a A/amvsu ATTORNEY SECONDARY BLASTING CHARGE AND CONTAINER 'rnensron BACKGROUND AND PRIOR ART ln mining operations there are frequent instances where broken ore or other rock gets hung up in a shaft or stope, etc., instead of falling to a desired delivery point. In other cases, some rocks which are not completely removed from a formation, or which project in passage ways, etc., may seriously impede further mining operations. Related problems may be encountered in construction projects. In the prior art it has been common practice to remove such obstacles, e.g., hang-ups, or interfering formations by secondary blasting, i.e., by placing secondary blasting charges on or against the protruding formation. Cans of explosive, bundles of stick-type explosives,

'7 shaped charges, and the like have been used or suggested for use in this manner. One common procedure has been to make up a charge of a number of sticks of dynamite wrapped in paper. This packaged charge is propped against the formation by use of a supporting stick or pole which is lashed to the package. Subsequently the charge is detonated with an appropriate cap, detonating fuse, or other initiator.

The secondary blasting devices previously used often are not convenient for the purpose. Some of them are difficult to hold in place. Paper-wrapped packages or bags frequently rupture and spill the dynamite sticks or other explosive material, causing inconvenience as well as creating possibly serious and unnecessary hazards. Tying the conventional package to the stick is itself an inconvenience and the tie does not always hold. It is highly desirable to have available a secondary blasting charge which is more convenient to handle, which can be set up easily and quickly and propped firmly and reliably against the rock to be blasted, and held there stably, i.e., on the end of a stick or pole. The charge should be so arranged so that it can be held in place without any particular tying or other special fastening.

According to the present invention, such a charge, which may comprise solid, slurry or liquid explosive material, is packaged in a container of suitable size and shape which conreceiving not only a supporting stick or pole, but also for containing the detonator and positively holding it in position in an inner or central part of the explosive charge, to insure reliable detonation. The container itself preferably is so shaped as to optimize the blasting effect of a charge of given weight. The package and detonator are designed not only for safer handling but also to ensure that effective detonation will surely occur. The latter is accomplished preferably by shaping and sizing the recess or pocket element, which is designed for receiving the supporting stick or pole to hold the initiator in place. Thus an effective initiator, which can be either a standard initiating cap when such is adequate for initiation, or preferably a length of detonating fuse such as Primaeord suitably conformed or attached to a booster, for less sensitive explosive charges, can be retained in the proper location. The initiator or booster in any case must be adequate in power to cause full detonation. For many types of explosive, such as prills and oil and some of the more sensitive blasting slurries, a length of detonating fuse is looped, coiled or knotted and secured to or over the end of a stick or pole so that it is properly positioned and securely held within the charge and in an effective detonating position at or near the center of mass of the main explosive charge.

tainer is provided with a special recess or pocket designed for SUMMARY A packaged charge of high explosive material consists of a container, preferably moistureproof, which encloses the explosive and has a pocket for snugly receiving and holding a 1X2 inch pole or stick. This pocket also receives and holds in proper position an initiating device. The package preferably has a frictional surface so that it is held securely in place against the rock to be blasted. The pocket element can be formed integrally and then cut off to serve as a closure for the filler opening.

DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of an assembled filled explosive package made according to the invention, as it is set up for use in blasting.

FIG. 2 is a similar view of the same package as it is molded DESCRIPTION OF PREFERRED EMBODIMENT Referring first to FIGS. 1, 2, and 3 of the drawings, a generally rectangular hollow container 1 is formed, preferably molded or blown from a suitable plastic composition, with a unitary pocket or stem element 2 depending or otherwise extending therefrom. This container, the main body of which is adapted to hold an explosive charge, may be made in any conventional manner, of any suitable plastic, reinforced plastic, fibrous material, or metal. Preferably it is blow-molded from a thermoplastic or thermosetting resin in a separable two-part or multipart mold. High-density polyethylene or a similar moldable resin is presently preferred. Obviously other olefin polymers, polystyrenes, vinyl compounds, urea-formaldehyde resins and the like may be used. The material should have high-impact strength so that it will not be easily broken if dropped on rocks, for example.

The stem element 2 preferably is molded integrally with the body 1 and is formed with an external rib or reinforcing flange 3 adjacent to the main body of the container 2, see FIG. 2. It has a second external rib or flange 4 spaced from flange 3 by a neck portion 5. This stem or pocket element 2 is adapted to be removed from the main container 1, e.g., by cutting it off after it is molded, to become a dual function element, namely a receiving pocket for a supporting pole or stick 6 and a closure for the opening in the main container. It is rectangular in cross section to fit the stick 6 and is slightly tapered so that the stick becomes progressively tighter as it is pushed into the pocket, as seen in FIGS. 1 and 3. The terminal end of the stem 2 is somewhat pointed to facilitate its insertion into a filled con tainer l, which may contain prills and oil, viscous slurry, or other suitable blasting agent. The stem or pocket element is designed to be cut off, preferably at the neck portion 5 along a line 8, FIG. 2.

The stem 2 is provided on each of its broader faces with a protruding lock element in the form of a rib or boss 7. After the stem is cut off at or about line 8, the container is filled with explosive, the stem 2 is used as a stopper or plug for the filler opening. It is pushed pointed end first into the opening formed by the cutting operation, that is, its formerly bottom end (as seen in FIG. 2) is inserted into the container. This pointed bottom end of the pocket member 2 serves as a receptacle to receive an initiating device such as a cap, booster, or a piece of detonating fuse 9. The latter should be knotted or wound into a small coil which is pushed deep into the pocket, i.e., to the top of the stem, as seen in FIGS. 1 and 3, before the supporting pole 6 is inserted into the pocket or stem member 2.

It will be understood that the parts are so dimensioned that the initiator, which may be a coiled or knotted end of a detonating fuse 9, as already mentioned, for prills and oil explosives, or a cap when the container is filled with sensitive explosive, or a booster attached to a detonating or igniting fuse, for the very insensitive explosives such as some of the aqueous slurries, will be located at about the center of the blasting charge which fills the main container 1. The initiator must, of course, be sufficiently powerful to detonate the filler charge. After the container 1 is filled with the blasting composition, the stem of pocket member 2 is pushed into it through the tiller opening and is locked in place there by a resilient or snap engagement of the locking ribs or boss elements 7 within the flange 3, which is part of the main container 1. This not only provides security against accidental spilling of the explosive charge from the main container, but also holds the container firmly on top of the supporting pole or stick 6. Also, the insertion of this pole or stick in the pocket or stem member 2, locks in place the fuse or detonating cord and any initiator or booster which is used. This arrangement makes certain that the initiator device will be positioned in or near the center of the main explosive charge. This assures reliable detonation of the charge when the initiator is fired. The walls of the pocket member 2 are made quite thin so as not to interfere with detonation and, of course, they are completely surrounded by the main charge. The thickness of the main container walls, as well as those of the pocket element 2, may vary somewhat from as little as a few thousandths to as much as several hundredths of an inch. Preferably, the walls of the main container are thick enough to support the weight of the charge without bending or folding to any substantial degree but the walls of the pocket element must not be so thick as to interfere with successful detonation of the charge when the initiator is fired.

The walls of the main container 1 are preferably embossed or molded with a pattern which will enhance their friction (1 when the containers are stacked on one another and (2) increase their friction against sliding or slipping along the surface of a mass of rock to be blasted. A suitable embossing pattern is shown in FIGS. 1 and 2 but other patterns may be used so long as the desired frictional surface is obtained.

If desired, frictional materials may be secured to or molded into the container walls in lieu of or in addition to embossing. Thus, particles of sand, strips of sandpaper or analogous materials may be secured adhesively, or in the molding process where special frictional properties are desired. Ordinarily the molded roughened or irregular surface is sufficient. Containers may be stacked together and the embossed or frictional surfaces prevent sliding and slipping on each other, as well as sliding and slipping on the rock surfaces against which they are propped by sticks or poles 6.

According to another modification of the-invention, a thinwalled container 10, is shown in FIG. 4 which is made up of a moldable plastic material, such as polyethylene, polypropylene, vinyl polymer, or any similar or suitable material of types mentioned above, capable of being shaped or fabricated economically. The package, as seen in FIG. 4, is more or less rectangular in form, to give a near optimum shape to the charge which it holds, preferably having rounded corners to facilitate molding. Four of its six rectangular faces are preferably uninterrupted by openings, two or more of these surfaces being embossed to give frictional surfaces but otherwise planar except for the rounded corners previously mentioned. Thus the larger sides 11 and 13, as seen in FIG. 4, may be embossed or roughened over most of their areas; the rear and the front ends or surfaces 15, 17 are somewhat smaller in area and are in planes generally perpendicular to the other faces, as seen in FIG. 4. These may or may not be provided with roughened or frictional surfaces. The front end or face 17, as seen in FlG. 4, may have a lightlyflanged filler opening 21. adapted to receive and hold by friction a closure disc or stopper 23. This disc can be removed for filling with explosive and replaced to retain the contents. The explosive to be used for filling may be either a granular-type material, such as ammonium nitrate prills sensitized with a smaller amount of fuel oil, other particulate or stick explosives of various kinds, such as pelleted TNT, granulated black powder or other conventional dry or solid explosive materials. An aqueous ammonium nitrate blasting slurry containing finely divided aluminum and/or other fuel-sensitizers, of the general type described for example, in US. Re. Pat. No. 25,695, may be used. The explosive material may be cap-sensitive, that is, subject to detonation by a standard primer cap or a length of detonating fuse such as Primacord." The detonating fuse may be knotted or looped to increase its effect as an initiator, or a more powerful and separate booster may be used. If the explosive is not capsensitive, a booster of some kind must be used. Either a cap, booster or" Primacord," etc.,"may be inserted in the pocketlike opening 30 in a sidewall 25. The latter opening preferably is approximately of a shape shown in detail in FIGS. 4, 5, and

, 6. It is adapted, like the pocket 2 of FIG. 1, to receive a pole or stick 40, as shown in FIGS. 5 and 6, so as to prop the explosive charge securely in place for blasting, preferably with one of its larger side faces 11 or 13 lying flush or as closely as possible against the rock to be blasted away. This pocket, like pocket 2 described above, is sized to receive snugly the end of a 1X2- inch stick 40, preferably because such sticks are inexpensive and widely available, but other sizes may be provided for.

If the obstacle to be removed is a hang-up of broken rock or a piece of rock hanging from a ceiling, the charge may be placed directly under it, preferably with a major friction-surfaced face 11 or 13 in contact. Protrusions which block or partially block tunnels or shafts, etc., in any position may be blasted away by setting the charge against a face of the rock to be removed, propping it there with a stick 40 broken or cut to suitable length if necessary, inserted in the opening 30, and then detonating. A similar arrangement is used for the package of FIG. 1, the main difference being the arrangement and manner of making of attaching the pocket element to the package.

The opening or cavity 30 is shaped so as not only to receive snugly the support or prop stick 40, as is shown, but also to hold the initiator or detonating device in close proximity to an internal part of the explosive charge. By providing a slight arching in the broader walls of the opening or cavity 30, for example the sidewall 33 and the opposite wall 34, the cavity 30 is reinforced against collapse due to pressure of the explosive material in the main package. This shape or manner of formation of cavity 30 thus keeps the cavity open and ready to receive the support stick. While this arrangement is preferred, other shapes and formations of pocket opening or cavity can be used in some cases.

At its inner end the cavity or recess 30 may be provided with a small arch or protuberance 36, see especially FIG. 6, which is adapted to receive a detonator or booster 50 in addition to the pole or stick 40. The detonator or initiator, as previously explained, may be a cap, a small mass of sensitive explosive plus a cap, or a booster inserted in or at the end of the stick. As already mentioned a loop or knot of Primacord" or equivalent detonating fuse 50, doubled or folded, etc., at 51 to increase its power, is placed over the end of the stick and pushed into place. As shown in FIG. 5 and indicated in dotted lines in FIG. 6, the knot can be arranged at the side of the top end of the stick or partly overlying its upper end.

The dimensions of the container 10 may be varied con siderably. For typical uses in underground mines, a container which will hold in the neighborhood of one U.S. gallon or about 200 to 250 cubic inches of explosive material is a useful size; however, the container may be somewhat smaller or much larger as will be obvious to those skilled in the art. The cavity 30 preferably is tapered slightly to hold the stick 40 with increasing friction as it is inserted and the knot 51 or the detonating cord itself can serve further to wedge or tighten the stick 40 in the cavity.

Containers which can readily be blow-molded, are relatively cheap and highly satisfactory for the purpose. Such are particularly suitable for the purposes of the present invention, since the container itself as well as the charges and all materials associated therewith are necessarily expendable. A separate filler opening analogous to filler opening 21 can be used in the container of FIG. 1; likewise, the container of FIGS. 4 to 6 can be formed so that the pocket element 30, 34, etc., is separable, to serve both as a stick and fuse receiving pocket and as a closure for the filler opening.

in use, the container 1 or 10 is first filled with the desired explosive, which may be of any suitable type, as already noted. The filled container is placed on the stick or pole 6 or 40 which fits into the cavity 30, preferably sufficient fully or tightly to prevent inadvertent slipping or falling of the package. The pole or stick is made of suitable length to be propped or supported against the ground or against a sidewall and may be bowed to apply a resilient holding pressure. The stick is set to hold the package against the rock to be broken, preferably with one of the larger flat faces 11 or 13 lying as closely against the rock as is practicable. The detonating cord 50, knotted at its end and looped over the end of the stick 6 or 40, or attached to a larger booster if needed, can be connected at its other end to an electric blasting cap or other primary initiator 52, or a conventional timing fuse can be used, as will be obvious. The charge can also be detonated directly by any suitable means such as an electric cap, placed on the inner end of the pole 6 or 40 and attached to wires which are looped over the pole. The detonator should be located as close as convenient to the center of the mass of explosive inside the container, preferably being closely confined to maximize its detonatin g effect. It is separated from the explosive, of source,

only by a thin section 60 of the plastic wall; see FIG. 3. With this arrangement there is no possibility that the charge will fail to detonate.

The package may assume other shapes and forms. e.g., cylindrical, spherical, etc. Preferably it is shaped so as to place a major part of its mass closely adjacent to the formation which is to be broken. The pocket element, whether molded integrally outside or inside, or molded separately as it may be is formed so as to retain the supporting stick with stability and also to provide a pocket which will hold the initiator in an effective position relative to the container contents to insure reliable detonation thereof. These principles should apply regardless of changes in form or dimensions. The pocket should be sufficiently strong or reinforced to resist collapse or inversion by reason of the weight or pressure of the contents of the main container.

It is intended by the claims which follow, to cover such apparent and obvious modifications and variations as would occur to those skilled in the art, as fully as the prior art properly permits.

What is claimed is:

1. A blasting charge comprising a molded plastic container having a main body filled with a blasting charge of explosive material, said main body having a hole in a bottom wall plugged with a reversed hollow pole receiving stern, a primer in the stem and outside of said blasting charge, said primer being adapted to be retained in the stem by a supporting pole, said stem being severed by cutting from an original unitary main body and projecting stern, whereby the severing of the stem from the main container body provides said hole. 

1. A blasting charge comprising a molded plastic container having a main body filled with a blasting charge of explosive material, said main body having a hole in a bottom wall plugged with a reversed hollow pole receiving stem, a primer in the stem and outside of said blasting charge, said primer being adapted to be retained in the stem by a supporting pole, said stem being severed by cutting from an original unitary main body and projecting stem, whereby the severing of the stem from the main container body provides said hole. 